Modern automatic weapons over the full caliber range make use of a variety of mechanisms for feeding the cartridges into the breech of the weapon. Mention may be made, in this connection, of magazine feeders, turret feeders and belt feeders. Of concern to the present invention, however, are belt-feeding mechanisms for such automatic weapons.
In addition, mention may be made of the various ways in which the belt can be advanced, e.g. by the use of recoil energy or by gas power. It is an advancing system of the latter type with which the present invention is concerned.
In gas-powered belt-advancing mechanisms for belt-fed automatic weapons, such as machine guns, an energy-flow path can be provided which at its input side, is formed by a gas passage for tapping the high pressure of the gas propellant which drives the bullet or projectile from the barrel of the weapon upon the firing thereof.
The gas passage feeds a cylinder/gas-piston unit which converts the energy of the propellant gas (pneumatic energy) into mechanism energy, the output of the gas piston being applied to a ratchet pawl and a transport shaft for stepping the belt and aligning the next cartridge thereof with the breech or cartridge chamber.
A time-delay unit is provided in this energy-flow train in the form of a mechanical energy storage device, e.g. which can have springs compressible by the pneumatic energy.
The belts which are used in such automatic weapons generally are formed as a flexible element or with a plurality of articulated links and have spaced apart seats, e.g. in the form of clips, into which the respective cartridges can be pressed.
The gas-pressure loading utilizes the highly compressed propellant gas behind the projectile and branches a small fraction of the volume of this propellant gas from the barrel behind the projectile upon the firing thereof and before the projectile has fully escaped from the barrel of the weapon.
When such compressed gas is used to actuate accessories of the weapon, e.g. the cartridge-feed ratchet pawl and the belt-displacement shaft, care must be taken to bear in mind the mass of the belt and hence its inertia.
The problem is that the gas pressure pulse is only applied for a brief instant during each firing cycle.
Because of its inertia or mass of the belt, the latter responds to forces tending to advance the belt, especially if they are practically instantaneous by a retardation which applies considerable stress to the belt. These stresses may cause tearing of the belt.
In German Pat. No. 1,290,455 there is described a system which is intended to avoid this disadvantage. In this system, the gas pressure upon firing of the weapon is recovered as pneumatic energy and the pneumatic energy is, in turn, transformed into mechanical energy in a cylinder/gas-piston unit. The gas piston actuates in its working stroke a ratchet pawl which is provided with a restoring spring and the ratchet, in turn, stresses a plurality of spirally coiled, prestressed band-type coil springs which collectively form a stack serving as a force-storage device.
After the stored energy reaches a certain level, it is applied to a belt-feed mechanism, for example via a shaft.
This system has the advantage, because of the conversion of the gas pressure into mechanical energy which is stored, that the stored mechanical energy can effect the advance of the loading belt in a highly reproducible and reliable manner because mechanical energy can be recovered from storage over a fixed path and for a fixed interval fully reproducibly over many operating cycles. However, it has the disadvantage that the time required for stressing the energy-storage spring and recovering the energy from the mechanical storage is considerable and, if reduced or eliminated, could enable the advance of the belt more rapidly, i.e. allow the transmission of energy along the path from the rise of the pneumatic pressure (i.e. the generation of the energy pulse) to the actuations of the advancing mechanism for the belt to be shortened.
This is particularly important for automatic weapons which are to have a high fire power and hence a more rapid loading cadence and rounds per minute firing capability than lower fire-power weapons.
In addition, the increased length of the energy transmission train of necessity involves a number of mechanical components which increase the fabrication cost of the weapon, the maintenance operation required for it and the complexity with concomitant danger of decreased reliability. Another disadvantage of the longer energy train is, of course, the increased size and weight of the weapon.
In practice, it has been found that the storage spring systems of the earlier weapons require frequent checking to avoid malfunctioning due to settling.
Finally, a disadvantage of the earlier systems is a need for a large number of parts which tend to wear and must be replaced so that logistical problems can arise in the use of such weapons.